Sorry! I meant to say 'bighall' not 'tallroom.'
Extract 'meshes\dungeons\neoclassical\bighall' to your NV data folder instead.
Also make sure you have your archive invalidation activated.
Now, I don't know if you have knowledge of Nifskope and the .nif file format, which is what Bethesda uses to package assets or meshes for the game, but if you do, then good.
For some reason, each of the .nifs in the '\neoclassical\tallroom' folder has an NiAlphaPropety attached to the node for the walls/ceilings. You'll notice that the walls themselves aren't white, but that you're actually looking through them into a white 'void.' This is truly befuddling to me because it seems not everyone is running the same version of the game and that these meshes either come with this extra property or they don't. In other words, my install of Fallout 3 does not include the same resources that yours does.
1) For a quick fix, since you have photoshop, locate the following texture
'textures\dungeons\neoclassical\NeoclassicalMainTile03.dds'
extract it, and delete it's alpha channel (or fill it white: 255,255,255).
2) OR you can open up each of the twenty .nifs in the 'bighall' folder and go through and delete the NiAlphaProperty from the nodes in question.